1. Field of the Invention
The present invention relates to devices for holding or widening tubular interlocking stranded rope or cable or of placing protuberances or bulges thereon which are immovable longitudinally along the rope. The bulge increases the diameter of the rope to create, for example, an abutment that prevents longitudinal movement of the rope past a mating abutment or stop member.
The words braid, plait, weave, intertwine, interlace or mesh have some similarity of meanings. For purposes of this patent they are deemed to be exactly synonymous. Herein they mean a number of strands or strand groups united to form a rope by intercrossing or stitching or passing over and under each other such that a rod passing transversely through the rope so formed is immovable longitudinally along the rope. Such rope has a set of such stitches arrayed in a circle on a transverse plane through the rope, with numerous such sets of stitches along the length of the rope. Any stitch or set of stitches sufficiently away from an end of the rope is substantially immovable longitudinally of the rope so that if lengthwise strain is placed upon a stitch or set of stitches on a common transverse plane, the stitches will not unravel. Therefore, there will be no decrease in the number of stitches upstream of the point of, or transverse plane of lengthwise strain, although the upstream stitches may crowd. And therefore, the strands or strand groups of such rope may be said to interlock and such rope exhibits a locking phenomenon. This invention is for use with such interlocking stranded rope, and not for use with twisted rope having no stitches.
The word tubular herein means a rope in which the strands or strand groups thereof can be arranged to substantially surround an object. This invention is for use with tubular rope.
That is, the type of rope intended to be used with this invention is tubular interlocking stranded rope as hereinabove defined.
2. Description of the Prior Art
Reduced to its most fundamental function, wherever rope is used, its purpose is to prevent two objects from moving apart more than a maximum distance from each other. Therefore, to be useful, a rope must be held at at least two points. To accomplish this objective, rope must be connected to each object, with one object connected at one point on the rope and the other connected at a point longitudinally spaced from the first point of connection. All prior methods or devices of connection known to this inventor, such as knots, eye splices or transverse rods throught the rope, have weakened the rope--that is, decreased its resistance to tension. Furthermore, this inventor knows of no rope bulging method or connecting or widening device which employs the locking phenomenon of tubular interlocking stranded rope as described herein, either alone or in combination with pressing surfaces, except that described in this inventor's U.S. Pat. No. 4,458,389.
U.S. Pat. No. 2,032,567, Feige, discloses a cable hitch with a two-part cavity, threadably secured, enclosing a cable expanded over a wedging element. The wedging element has a downstream convex conical taper and has lands and grooves along its entire length, in which the strand groups partially nest. The cavity has only one aperture which is downstream of the wedging element and which is large enough to allow an unexpanded portion of the cable to pass therethrough, but too small to allow the portion of the cable expanded over the wedging element to pass therethrough. The upstream end of the cavity is a closed cup containing the freyed cable ends. The cable is pressed downstream and clamped between the downstream convex conical taper of the wedging element and the downstream concave frustum of the cavity during the process of threading the cavity portions together. The freyed cable ends are also bent over and twisted around the upstream end of the wedging element as the cavity portions are threaded together. Feige's cable hitch is not suitable for use with woven rope because it lacks an upstream aperture so that there would be insufficient rope upstream of the wedging element for the locking phenomenon of woven rope to occur upon the application of tension; and because the longitudinal grooves are shallower than the diameters of the individual strand groups, a given pick or stitch or strand group crossover point could not be maintained upstream of the upstream edge of a land because the strand groups would be pulled downstream over the tops of the lands, as will be more fully explained. It should be noted that the Fiege termination can only be used on an end point while the subject rope widening apparatus can only be used at an intermediate point.
U.S. Pat. No. 2,935,776, Clark, discloses a Cable Shackle with a one piece open cavity. The cavity is a concave frustum surface with the narrow opening downstream. The cavity contains a core portion with a plurality of elongated helical grooves along its entire periphery. The core portion is divided longitudinally into two wedge pieces forming a longitudinally divided elongated bore whose axis is coincident with the axis of the core portion. The elongated bore is for gripping the center unconvoluted core strand of a cable, while the helical grooves on the periphery receive the convoluted strands of the cable which wind helically about the unconvoluted core strand. The helical grooves on the periphery of the core portion are only partially as deep as the diameters of the convoluted cable strands. Thus, when the cable, expanded over the core portion, is wedged into the concave frustum of the cavity, the convoluted strands are firmly held. Also, the elongated bore has a shorter diameter than the diameter of the unconvoluted core strand, thus the sides of the elongated bore grip the core strand when the wedge pieces are forced together by being wedged into the concave frustum of the cavity. The Clark Cable Shackle is not suitable for use with woven rope because the helical grooves on the periphery of the core portion spiral in one direction, while the strand groups of woven rope spiral in two opposite directions, so that the helical grooves could not accept those strand groups of woven rope which spiral in the direction opposite of the helical grooves without creating bending stresses where the strand groups touch the upstream and downstream ends of the grooves; and, since the helical lands are shorter than the diameters of the individual strand groups, a given pick or stitch or strand group crossover point could not be maintained upstream of the upstream edge of a land because the strand groups would be pulled downstream over the tops of the lands, as will be more fully explained.
The aforementioned two inventions of Fiege and Clark are for use with twisted--not woven--steel wire cable. Steel wire cable is not as pliant as fabric rope made of such materials as nylon, polyethelyne or polypropolene. Because of its flexibility, light weight and cushioned surface, fabric rope is used where steel cable is not appropriate. For example, steel wire cable can mar polished boat hulls. Also, because of its stiffness, steel wire cable cannot be stored as compactly as fabric rope. Woven fabric rope, because the strand groups interweave and spiral in two opposite directions, cannot hockle as can twisted fabric rope. It is therefore desireable to use woven fabric rope and find a device to hold it without creating a weakness.
It is this inventor's experience that twisted pliant rope can be held only with knots and eye splices, both of which have a greater or lesser weakening effect. It is generally known that knots weaken a rope by 50% because of the bending stresses, and eye splices have a slight weakening effect. In this inventor's experiments with twisted pliant fabric rope (as distinguished from woven rope) using longitudinally grooved wedging elements similar to those in the aforementioned Fiege and Clark patents, the rope was pulled through the grooves rather than held in the fixture until the rope broke. Apparently this does not occur with twisted steel cable, possibly because the wires bite into the wedging elements or the wedging elements may have teeth to bite into the cable strands. For example, Fiege, in another patent, U.S. Pat. No. 1,958,747, shows thin circumferential grooves that apparently bite into the wire strands. However, the edges of such circumferential grooves would cut fabric rope strands.
Other devices similar to those of Fiege or Clark for holding steel wire cable in which the grooves in the wedging element are shallower than the diameters of the cable strands and/or in which the grooves spiral in only one direction, are shown in U.S. Pat. Nos. 1,909,332; 2,017,887; 3,600,765; 4,055,365; French Pat. No. 1,450,345; British Pat. Nos. 512,893 and 1,056,990.